A field, as used in this application and in the audio/visual arts in general, is a frame or guide drawn around a two-dimensional display which is to be photographed, to aid the photographer in lining up his camera. The guide may be drawn directly around the display or, more usually, on a piece of tissue paper attached over the display. The ratio of the width to length of the frame is determined by the ratio of the width to the length of the photographic material on which the display is to be reproduced.
In photographing the exhibit the photographer need only use the frame as a guide in his previewing device to see what will finally result on his negative. In addition, the person setting up the display can control the cropping of the exhibit, or at least be aware of that cropping which will occur by reason of the photographic material format or size being used to reproduce the exhibit.
There are a number of ways in which a field of proper width to length ratio is drawn. However, these methods are generally quite cumbersome. For example, one method utilizes a T-square and triangle; a second method uses a relatively expensive and cumbersome L-device known as a scalograph, while a third method utilizes a sheet of acetate on which are predrawn a number of fields which can be traced.
Basically the T-square and triangle method requires drawing arbitrary upper and lower horizontal lines plus one arbitrary vertical line and thereafter measuring ratios on these lines. A diagonal is drawn and the proper ratio marked thereon to be used as a guide for drawing the field.
The double L-device or scalograph is basically two angle guides connected together by a diagonal which keeps them aligned properly.
The third method, the use of a solid acetate sheet with predrawn fields, requires that one lay the sheet over the exhibit to be cropped and lay a piece of tissue paper over the sheet. The appropriate field most closely approximating the desired cropping outline is then traced onto the tissue paper.
The usual methods employed for forming a field suffer from a number of disadvantages. The T-square and triangle method, although reasonably accurate, requires a great deal of careful work to obtain proper results. The scalograph is relatively expensive and not very accurate or precise in operation. The use of a sheet of acetate with predawn fields, although relatively inexpensive, is also relatively inaccurate in that it requires a step wherein someone will need to trace a field onto a sheet of tissue and also requires a determination as to which field is closest to that which is desired.
It is an object of the present invention to provide a cropping guide which, although relatively inexpensive to manufacture and simple to operate, is accurate and precise.
It is a further object to provide a cropping guide which can be used to draw a field having a certain ratio as to its width to length, but of any required absolute size.
It is a still further object of the invention to provide a cropping guide which will allow quick and simple determination of the center of the field being drawn.
Other objects will be brought out below or will be obvious therefrom.